A64: add missing files.

src/a64/regexp-macro-assembler-a64.cc

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#if defined(V8_TARGET_ARCH_A64)
+
+#include "unicode.h"
+#include "log.h"
+#include "code-stubs.h"
+#include "regexp-stack.h"
+#include "macro-assembler.h"
+#include "regexp-macro-assembler.h"
+#include "a64/regexp-macro-assembler-a64.h"
+
+namespace v8 {
+namespace internal {
+
+#ifndef V8_INTERPRETED_REGEXP
+/*
+ * This assembler uses the following register assignment convention:
+ * - w19     : Used to temporarely store a value before a call to C code.
+ *             See CheckNotBackReferenceIgnoreCase.
+ * - x20     : Pointer to the current code object (Code*),
+ *             it includes the heap object tag.
+ * - w21     : Current position in input, as negative offset from
+ *             the end of the string. Please notice that this is
+ *             the byte offset, not the character offset!
+ * - w22     : Currently loaded character. Must be loaded using
+ *             LoadCurrentCharacter before using any of the dispatch methods.
+ * - x23     : Points to tip of backtrack stack.
+ * - w24     : Position of the first character minus one: non_position_value.
+ *             Used to initialize capture registers.
+ * - x25     : Address at the end of the input string: input_end.
+ *             Points to byte after last character in input.
+ * - x26     : Address at the start of the input string: input_start.
+ * - w27     : Where to start in the input string.
+ * - x28     : Output array pointer.
+ * - x29/fp  : Frame pointer. Used to access arguments, local variables and
+ *             RegExp registers.
+ * - x16/x17 : IP registers, used by assembler. Very volatile.
+ * - csp     : Points to tip of C stack.
+ *
+ * - x0-x7   : Used as a cache to store 32 bit capture registers. These
+ *             registers need to be retained every time a call to C code
+ *             is done.
+ *
+ * The remaining registers are free for computations.
+ * Each call to a public method should retain this convention.
+ *
+ * The stack will have the following structure:
+ *
+ *  Location    Name               Description
+ *              (as referred to in
+ *              the code)
+ *
+ *  - fp[104]   isolate            Address of the current isolate.
+ *  - fp[96]    return_address     Secondary link/return address
+ *                                 used by an exit frame if this is a
+ *                                 native call.
+ *  ^^^ csp when called ^^^
+ *  - fp[88]    lr                 Return from the RegExp code.
+ *  - fp[80]    r29                Old frame pointer (CalleeSaved).
+ *  - fp[0..72] r19-r28            Backup of CalleeSaved registers.
+ *  - fp[-8]    direct_call        1 => Direct call from JavaScript code.
+ *                                 0 => Call through the runtime system.
+ *  - fp[-16]   stack_base         High end of the memory area to use as
+ *                                 the backtracking stack.
+ *  - fp[-24]   output_size        Output may fit multiple sets of matches.
+ *  - fp[-32]   input              Handle containing the input string.
+ *  - fp[-40]   success_counter
+ *  ^^^^^^^^^^^^^ From here and downwards we store 32 bit values ^^^^^^^^^^^^^
+ *  - fp[-44]   register N         Capture registers initialized with
+ *  - fp[-48]   register N + 1     non_position_value.
+ *              ...                The first kNumCachedRegisters (N) registers
+ *              ...                are cached in x0 to x7.
+ *              ...                Only positions must be stored in the first
+ *  -           ...                num_saved_registers_ registers.
+ *  -           ...
+ *  -           register N + num_registers - 1
+ *  ^^^^^^^^^ csp ^^^^^^^^^
+ *
+ * The first num_saved_registers_ registers are initialized to point to
+ * "character -1" in the string (i.e., char_size() bytes before the first
+ * character of the string). The remaining registers start out as garbage.
+ *
+ * The data up to the return address must be placed there by the calling
+ * code and the remaining arguments are passed in registers, e.g. by calling the
+ * code entry as cast to a function with the signature:
+ * int (*match)(String* input,
+ *              int start_offset,
+ *              Address input_start,
+ *              Address input_end,
+ *              int* output,
+ *              int output_size,
+ *              Address stack_base,
+ *              bool direct_call = false,
+ *              Address secondary_return_address,  // Only used by native call.
+ *              Isolate* isolate)
+ * The call is performed by NativeRegExpMacroAssembler::Execute()
+ * (in regexp-macro-assembler.cc) via the CALL_GENERATED_REGEXP_CODE macro
+ * in a64/simulator-a64.h.
+ * When calling as a non-direct call (i.e., from C++ code), the return address
+ * area is overwritten with the LR register by the RegExp code. When doing a
+ * direct call from generated code, the return address is placed there by
+ * the calling code, as in a normal exit frame.
+ */
+
+#define __ ACCESS_MASM(masm_)
+
+RegExpMacroAssemblerA64::RegExpMacroAssemblerA64(
+    Mode mode,
+    int registers_to_save,
+    Zone* zone)
+    : NativeRegExpMacroAssembler(zone),
+      masm_(new MacroAssembler(zone->isolate(), NULL, kRegExpCodeSize)),
+      mode_(mode),
+      num_registers_(registers_to_save),
+      num_saved_registers_(registers_to_save),
+      entry_label_(),
+      start_label_(),
+      success_label_(),
+      backtrack_label_(),
+      exit_label_() {
+  __ SetStackPointer(csp);
+  ASSERT_EQ(0, registers_to_save % 2);
+  // We can cache at most 16 W registers in x0-x7.
+  STATIC_ASSERT(kNumCachedRegisters <= 16);
+  STATIC_ASSERT((kNumCachedRegisters % 2) == 0);
+  __ B(&entry_label_);   // We'll write the entry code later.
+  __ Bind(&start_label_);  // And then continue from here.
+}
+
+RegExpMacroAssemblerA64::~RegExpMacroAssemblerA64() {
+  delete masm_;
+  // Unuse labels in case we throw away the assembler without calling GetCode.
+  entry_label_.Unuse();
+  start_label_.Unuse();
+  success_label_.Unuse();
+  backtrack_label_.Unuse();
+  exit_label_.Unuse();
+  check_preempt_label_.Unuse();
+  stack_overflow_label_.Unuse();
+}
+
+int RegExpMacroAssemblerA64::stack_limit_slack()  {
+  return RegExpStack::kStackLimitSlack;
+}
+
+void RegExpMacroAssemblerA64::AdvanceCurrentPosition(int by) {
+  if (by != 0) {
+    __ Add(current_input_offset(),
+           current_input_offset(), by * char_size());
+  }
+}
+
+void RegExpMacroAssemblerA64::AdvanceRegister(int reg, int by) {
+  ASSERT((reg >= 0) && (reg < num_registers_));
+  if (by != 0) {
+    Register to_advance;
+    RegisterState register_state = GetRegisterState(reg);
+    switch (register_state) {
+      case STACKED:
+        __ Ldr(w10, register_location(reg));
+        __ Add(w10, w10, by);
+        __ Str(w10, register_location(reg));
+        break;
+      case CACHED_LSW:
+        to_advance = GetCachedRegister(reg);
+        __ Add(to_advance, to_advance, by);
+        break;
+      case CACHED_MSW:
+        to_advance = GetCachedRegister(reg);
+        __ Add(to_advance, to_advance, static_cast<int64_t>(by) << kWRegSize);
+        break;
+      default:
+        UNREACHABLE();
+        break;
+    }
+  }
+}
+
+void RegExpMacroAssemblerA64::Backtrack() {
+  CheckPreemption();
+  Pop(w10);
+  __ Add(x10, code_pointer(), Operand(w10, UXTW));
+  __ Br(x10);
+}
+
+void RegExpMacroAssemblerA64::Bind(Label* label) {
+  __ Bind(label);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacter(uint32_t c, Label* on_equal) {
+  CompareAndBranchOrBacktrack(current_character(), c, eq, on_equal);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacterGT(uc16 limit, Label* on_greater) {
+  CompareAndBranchOrBacktrack(current_character(), limit, hi, on_greater);
+}
+
+
+void RegExpMacroAssemblerA64::CheckAtStart(Label* on_at_start) {
+  Label not_at_start;
+  // Did we start the match at the start of the input string?
+  CompareAndBranchOrBacktrack(start_offset(), 0, ne, &not_at_start);
+  // If we did, are we still at the start of the input string?
+  __ Add(x10, input_end(), Operand(current_input_offset(), SXTW));
+  __ Cmp(x10, input_start());
+  BranchOrBacktrack(eq, on_at_start);
+  __ Bind(&not_at_start);
+}
+
+
+void RegExpMacroAssemblerA64::CheckNotAtStart(Label* on_not_at_start) {
+  // Did we start the match at the start of the input string?
+  CompareAndBranchOrBacktrack(start_offset(), 0, ne, on_not_at_start);
+  // If we did, are we still at the start of the input string?
+  __ Add(x10, input_end(), Operand(current_input_offset(), SXTW));
+  __ Cmp(x10, input_start());
+  BranchOrBacktrack(ne, on_not_at_start);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacterLT(uc16 limit, Label* on_less) {
+  CompareAndBranchOrBacktrack(current_character(), limit, lo, on_less);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacters(Vector<const uc16> str,
+                                              int cp_offset,
+                                              Label* on_failure,
+                                              bool check_end_of_string) {
+  // This method is only ever called from the cctests.
+
+  if (check_end_of_string) {
+    // Is last character of required match inside string.
+    CheckPosition(cp_offset + str.length() - 1, on_failure);
+  }
+
+  Register characters_address = x11;
+
+  __ Add(characters_address,
+         input_end(),
+         Operand(current_input_offset(), SXTW));
+  if (cp_offset != 0) {
+    __ Add(characters_address, characters_address, cp_offset * char_size());
+  }
+
+  for (int i = 0; i < str.length(); i++) {
+    if (mode_ == ASCII) {
+      __ Ldrb(w10, MemOperand(characters_address, 1, PostIndex));
+      ASSERT(str[i] <= String::kMaxOneByteCharCode);
+    } else {
+      __ Ldrh(w10, MemOperand(characters_address, 2, PostIndex));
+    }
+    CompareAndBranchOrBacktrack(w10, str[i], ne, on_failure);
+  }
+}
+
+
+void RegExpMacroAssemblerA64::CheckGreedyLoop(Label* on_equal) {
+  __ Ldr(w10, MemOperand(backtrack_stackpointer()));
+  __ Cmp(current_input_offset(), w10);
+  __ Cset(x11, eq);
+  __ Add(backtrack_stackpointer(),
+         backtrack_stackpointer(), Operand(x11, LSL, kWRegSizeInBytesLog2));
+  BranchOrBacktrack(eq, on_equal);
+}
+
+void RegExpMacroAssemblerA64::CheckNotBackReferenceIgnoreCase(
+    int start_reg,
+    Label* on_no_match) {
+  Label fallthrough;
+
+  Register capture_start_offset = w10;
+  // Save the capture length in a callee-saved register so it will
+  // be preserved if we call a C helper.
+  Register capture_length = w19;
+  ASSERT(kCalleeSaved.IncludesAliasOf(capture_length));
+
+  // Find length of back-referenced capture.
+  ASSERT((start_reg % 2) == 0);
+  if (start_reg < kNumCachedRegisters) {
+    __ Mov(capture_start_offset.X(), GetCachedRegister(start_reg));
+    __ Lsr(x11, GetCachedRegister(start_reg), kWRegSize);
+  } else {
+    __ Ldp(w11, capture_start_offset, capture_location(start_reg, x10));
+  }
+  __ Sub(capture_length, w11, capture_start_offset);  // Length to check.
+  // Succeed on empty capture (including no capture).
+  __ Cbz(capture_length, &fallthrough);
+
+  // Check that there are enough characters left in the input.
+  __ Cmn(capture_length, current_input_offset());
+  BranchOrBacktrack(gt, on_no_match);
+
+  if (mode_ == ASCII) {
+    Label success;
+    Label fail;
+    Label loop_check;
+
+    Register capture_start_address = x12;
+    Register capture_end_addresss = x13;
+    Register current_position_address = x14;
+
+    __ Add(capture_start_address,
+           input_end(),
+           Operand(capture_start_offset, SXTW));
+    __ Add(capture_end_addresss,
+           capture_start_address,
+           Operand(capture_length, SXTW));
+    __ Add(current_position_address,
+           input_end(),
+           Operand(current_input_offset(), SXTW));
+
+    Label loop;
+    __ Bind(&loop);
+    __ Ldrb(w10, MemOperand(capture_start_address, 1, PostIndex));
+    __ Ldrb(w11, MemOperand(current_position_address, 1, PostIndex));
+    __ Cmp(w10, w11);
+    __ B(eq, &loop_check);
+
+    // Mismatch, try case-insensitive match (converting letters to lower-case).
+    __ Orr(w10, w10, 0x20);  // Convert capture character to lower-case.
+    __ Orr(w11, w11, 0x20);  // Also convert input character.
+    __ Cmp(w11, w10);
+    __ B(ne, &fail);
+    __ Sub(w10, w10, 'a');
+    __ Cmp(w10, 'z' - 'a');  // Is w10 a lowercase letter?
+    __ B(ls, &loop_check);  // In range 'a'-'z'.
+    // Latin-1: Check for values in range [224,254] but not 247.
+    __ Sub(w10, w10, 224 - 'a');
+    // TODO(jbramley): Use Ccmp here.
+    __ Cmp(w10, 254 - 224);
+    __ B(hi, &fail);  // Weren't Latin-1 letters.
+    __ Cmp(w10, 247 - 224);  // Check for 247.
+    __ B(eq, &fail);
+
+    __ Bind(&loop_check);
+    __ Cmp(capture_start_address, capture_end_addresss);
+    __ B(lt, &loop);
+    __ B(&success);
+
+    __ Bind(&fail);
+    BranchOrBacktrack(al, on_no_match);
+
+    __ Bind(&success);
+    // Compute new value of character position after the matched part.
+    __ Sub(current_input_offset().X(), current_position_address, input_end());
+    if (masm_->emit_debug_code()) {
+      __ Cmp(current_input_offset().X(), Operand(current_input_offset(), SXTW));
+      __ Ccmp(current_input_offset(), 0, NoFlag, eq);
+      __ Check(le,
+          "current_input_offset should be <= 0 and fit in a W register.");
+    }
+  } else {
+    ASSERT(mode_ == UC16);
+    int argument_count = 4;
+
+    // The cached registers need to be retained.
+    CPURegList cached_registers(CPURegister::kRegister, kXRegSize, 0, 7);
+    ASSERT((cached_registers.Count() * 2) == kNumCachedRegisters);
+    __ PushCPURegList(cached_registers);
+
+    // Put arguments into arguments registers.
+    // Parameters are
+    //   x0: Address byte_offset1 - Address captured substring's start.
+    //   x1: Address byte_offset2 - Address of current character position.
+    //   w2: size_t byte_length - length of capture in bytes(!)
+    //   x3: Isolate* isolate
+
+    // Address of start of capture.
+    __ Add(x0, input_end(), Operand(capture_start_offset, SXTW));
+    // Length of capture.
+    __ Mov(w2, capture_length);
+    // Address of current input position.
+    __ Add(x1, input_end(), Operand(current_input_offset(), SXTW));
+    // Isolate.
+    __ Mov(x3, Operand(ExternalReference::isolate_address(isolate())));
+
+    {
+      AllowExternalCallThatCantCauseGC scope(masm_);
+      ExternalReference function =
+          ExternalReference::re_case_insensitive_compare_uc16(isolate());
+      __ CallCFunction(function, argument_count);
+    }
+
+    // Check if function returned non-zero for success or zero for failure.
+    CompareAndBranchOrBacktrack(x0, 0, eq, on_no_match);
+    // On success, increment position by length of capture.
+    __ Add(current_input_offset(), current_input_offset(), capture_length);
+    // Reset the cached registers.
+    __ PopCPURegList(cached_registers);
+  }
+
+  __ Bind(&fallthrough);
+}
+
+void RegExpMacroAssemblerA64::CheckNotBackReference(
+    int start_reg,
+    Label* on_no_match) {
+  Label fallthrough;
+
+  Register capture_start_address = x12;
+  Register capture_end_address = x13;
+  Register current_position_address = x14;
+  Register capture_length = w15;
+
+  // Find length of back-referenced capture.
+  ASSERT((start_reg % 2) == 0);
+  if (start_reg < kNumCachedRegisters) {
+    __ Mov(x10, GetCachedRegister(start_reg));
+    __ Lsr(x11, GetCachedRegister(start_reg), kWRegSize);
+  } else {
+    __ Ldp(w11, w10, capture_location(start_reg, x10));
+  }
+  __ Sub(capture_length, w11, w10);  // Length to check.
+  // Succeed on empty capture (including no capture).
+  __ Cbz(capture_length, &fallthrough);
+
+  // Check that there are enough characters left in the input.
+  __ Cmn(capture_length, current_input_offset());
+  BranchOrBacktrack(gt, on_no_match);
+
+  // Compute pointers to match string and capture string
+  __ Add(capture_start_address, input_end(), Operand(w10, SXTW));
+  __ Add(capture_end_address,
+         capture_start_address,
+         Operand(capture_length, SXTW));
+  __ Add(current_position_address,
+         input_end(),
+         Operand(current_input_offset(), SXTW));
+
+  Label loop;
+  __ Bind(&loop);
+  if (mode_ == ASCII) {
+    __ Ldrb(w10, MemOperand(capture_start_address, 1, PostIndex));
+    __ Ldrb(w11, MemOperand(current_position_address, 1, PostIndex));
+  } else {
+    ASSERT(mode_ == UC16);
+    __ Ldrh(w10, MemOperand(capture_start_address, 2, PostIndex));
+    __ Ldrh(w11, MemOperand(current_position_address, 2, PostIndex));
+  }
+  __ Cmp(w10, w11);
+  BranchOrBacktrack(ne, on_no_match);
+  __ Cmp(capture_start_address, capture_end_address);
+  __ B(lt, &loop);
+
+  // Move current character position to position after match.
+  __ Sub(current_input_offset().X(), current_position_address, input_end());
+  if (masm_->emit_debug_code()) {
+    __ Cmp(current_input_offset().X(), Operand(current_input_offset(), SXTW));
+    __ Ccmp(current_input_offset(), 0, NoFlag, eq);
+    __ Check(le,
+        "current_input_offset should be <= 0 and fit in a W register.");
+  }
+  __ Bind(&fallthrough);
+}
+
+
+void RegExpMacroAssemblerA64::CheckNotCharacter(unsigned c,
+                                                Label* on_not_equal) {
+  CompareAndBranchOrBacktrack(current_character(), c, ne, on_not_equal);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacterAfterAnd(uint32_t c,
+                                                     uint32_t mask,
+                                                     Label* on_equal) {
+  __ And(w10, current_character(), mask);
+  CompareAndBranchOrBacktrack(w10, c, eq, on_equal);
+}
+
+
+void RegExpMacroAssemblerA64::CheckNotCharacterAfterAnd(unsigned c,
+                                                        unsigned mask,
+                                                        Label* on_not_equal) {
+  __ And(w10, current_character(), mask);
+  CompareAndBranchOrBacktrack(w10, c, ne, on_not_equal);
+}
+
+
+void RegExpMacroAssemblerA64::CheckNotCharacterAfterMinusAnd(
+    uc16 c,
+    uc16 minus,
+    uc16 mask,
+    Label* on_not_equal) {
+  ASSERT(minus < String::kMaxUtf16CodeUnit);
+  __ Sub(w10, current_character(), minus);
+  __ And(w10, w10, mask);
+  CompareAndBranchOrBacktrack(w10, c, ne, on_not_equal);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacterInRange(
+    uc16 from,
+    uc16 to,
+    Label* on_in_range) {
+  __ Sub(w10, current_character(), from);
+  // Unsigned lower-or-same condition.
+  CompareAndBranchOrBacktrack(w10, to - from, ls, on_in_range);
+}
+
+
+void RegExpMacroAssemblerA64::CheckCharacterNotInRange(
+    uc16 from,
+    uc16 to,
+    Label* on_not_in_range) {
+  __ Sub(w10, current_character(), from);
+  // Unsigned higher condition.
+  CompareAndBranchOrBacktrack(w10, to - from, hi, on_not_in_range);
+}
+
+
+void RegExpMacroAssemblerA64::CheckBitInTable(
+    Handle<ByteArray> table,
+    Label* on_bit_set) {
+  __ Mov(x11, Operand(table));
+  if ((mode_ != ASCII) || (kTableMask != String::kMaxOneByteCharCode)) {
+    __ And(w10, current_character(), kTableMask);
+    __ Add(w10, w10, ByteArray::kHeaderSize - kHeapObjectTag);
+  } else {
+    __ Add(w10, current_character(), ByteArray::kHeaderSize - kHeapObjectTag);
+  }
+  __ Ldrb(w11, MemOperand(x11, w10, UXTW));
+  CompareAndBranchOrBacktrack(w11, 0, ne, on_bit_set);
+}
+
+
+bool RegExpMacroAssemblerA64::CheckSpecialCharacterClass(uc16 type,
+                                                         Label* on_no_match) {
+  // Range checks (c in min..max) are generally implemented by an unsigned
+  // (c - min) <= (max - min) check
+  switch (type) {
+  case 's':
+    // Match space-characters
+    if (mode_ == ASCII) {
+      // One byte space characters are '\t'..'\r', ' ' and \u00a0.
+      Label success;
+      // Check for ' ' or 0x00a0.
+      __ Cmp(current_character(), ' ');
+      __ Ccmp(current_character(), 0x00a0, ZFlag, ne);
+      __ B(eq, &success);
+      // Check range 0x09..0x0d.
+      __ Sub(w10, current_character(), '\t');
+      CompareAndBranchOrBacktrack(w10, '\r' - '\t', hi, on_no_match);
+      __ Bind(&success);
+      return true;
+    }
+    return false;
+  case 'S':
+    // The emitted code for generic character classes is good enough.
+    return false;
+  case 'd':
+    // Match ASCII digits ('0'..'9').
+    __ Sub(w10, current_character(), '0');
+    CompareAndBranchOrBacktrack(w10, '9' - '0', hi, on_no_match);
+    return true;
+  case 'D':
+    // Match ASCII non-digits.
+    __ Sub(w10, current_character(), '0');
+    CompareAndBranchOrBacktrack(w10, '9' - '0', ls, on_no_match);
+    return true;
+  case '.': {
+    // Match non-newlines (not 0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029)
+    // Here we emit the conditional branch only once at the end to make branch
+    // prediction more efficient, even though we could branch out of here
+    // as soon as a character matches.
+    __ Cmp(current_character(), 0x0a);
+    __ Ccmp(current_character(), 0x0d, ZFlag, ne);
+    if (mode_ == UC16) {
+      __ Sub(w10, current_character(), 0x2028);
+      // If the Z flag was set we clear the flags to force a branch.
+      __ Ccmp(w10, 0x2029 - 0x2028, NoFlag, ne);
+      // ls -> !((C==1) && (Z==0))
+      BranchOrBacktrack(ls, on_no_match);
+    } else {
+      BranchOrBacktrack(eq, on_no_match);
+    }
+    return true;
+  }
+  case 'n': {
+    // Match newlines (0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029)
+    // We have to check all 4 newline characters before emitting
+    // the conditional branch.
+    __ Cmp(current_character(), 0x0a);
+    __ Ccmp(current_character(), 0x0d, ZFlag, ne);
+    if (mode_ == UC16) {
+      __ Sub(w10, current_character(), 0x2028);
+      // If the Z flag was set we clear the flags to force a fall-through.
+      __ Ccmp(w10, 0x2029 - 0x2028, NoFlag, ne);
+      // hi -> (C==1) && (Z==0)
+      BranchOrBacktrack(hi, on_no_match);
+    } else {
+      BranchOrBacktrack(ne, on_no_match);
+    }
+    return true;
+  }
+  case 'w': {
+    if (mode_ != ASCII) {
+      // Table is 128 entries, so all ASCII characters can be tested.
+      CompareAndBranchOrBacktrack(current_character(), 'z', hi, on_no_match);
+    }
+    ExternalReference map = ExternalReference::re_word_character_map();
+    __ Mov(x10, Operand(map));
+    __ Ldrb(w10, MemOperand(x10, current_character(), UXTW));
+    CompareAndBranchOrBacktrack(w10, 0, eq, on_no_match);
+    return true;
+  }
+  case 'W': {
+    Label done;
+    if (mode_ != ASCII) {
+      // Table is 128 entries, so all ASCII characters can be tested.
+      __ Cmp(current_character(), 'z');
+      __ B(hi, &done);
+    }
+    ExternalReference map = ExternalReference::re_word_character_map();
+    __ Mov(x10, Operand(map));
+    __ Ldrb(w10, MemOperand(x10, current_character(), UXTW));
+    CompareAndBranchOrBacktrack(w10, 0, ne, on_no_match);
+    __ Bind(&done);
+    return true;
+  }
+  case '*':
+    // Match any character.
+    return true;
+  // No custom implementation (yet): s(UC16), S(UC16).
+  default:
+    return false;
+  }
+}
+
+
+void RegExpMacroAssemblerA64::Fail() {
+  __ Mov(w0, FAILURE);
+  __ B(&exit_label_);
+}
+
+
+Handle<HeapObject> RegExpMacroAssemblerA64::GetCode(Handle<String> source) {
+  Label return_w0;
+  // Finalize code - write the entry point code now we know how many
+  // registers we need.
+
+  // Entry code:
+  __ Bind(&entry_label_);
+
+  // Arguments on entry:
+  // x0:  String*  input
+  // x1:  int      start_offset
+  // x2:  byte*    input_start
+  // x3:  byte*    input_end
+  // x4:  int*     output array
+  // x5:  int      output array size
+  // x6:  Address  stack_base
+  // x7:  int      direct_call
+
+  // The stack pointer should be csp on entry.
+  //  csp[8]:  address of the current isolate
+  //  csp[0]:  secondary link/return address used by native call
+
+  // Tell the system that we have a stack frame.  Because the type is MANUAL, no
+  // code is generated.
+  FrameScope scope(masm_, StackFrame::MANUAL);
+
+  // Push registers on the stack, only push the argument registers that we need.
+  CPURegList argument_registers(x0, x5, x6, x7);
+
+  CPURegList registers_to_retain = kCalleeSaved;
+  ASSERT(kCalleeSaved.Count() == 11);
+  registers_to_retain.Combine(lr);
+
+  ASSERT(csp.Is(__ StackPointer()));
+  __ PushCPURegList(registers_to_retain);
+  __ PushCPURegList(argument_registers);
+
+  // Set frame pointer in place.
+  __ Add(frame_pointer(), csp, argument_registers.Count() * kPointerSize);
+
+  // Initialize callee-saved registers.
+  __ Mov(start_offset(), w1);
+  __ Mov(input_start(), x2);
+  __ Mov(input_end(), x3);
+  __ Mov(output_array(), x4);
+
+  // Set the number of registers we will need to allocate, that is:
+  //   - success_counter (X register)
+  //   - (num_registers_ - kNumCachedRegisters) (W registers)
+  int num_wreg_to_allocate = num_registers_ - kNumCachedRegisters;
+  // Do not allocate registers on the stack if they can all be cached.
+  if (num_wreg_to_allocate < 0) { num_wreg_to_allocate = 0; }
+  // Make room for the success_counter.
+  num_wreg_to_allocate += 2;
+
+  // Make sure the stack alignment will be respected.
+  int alignment = masm_->ActivationFrameAlignment();
+  ASSERT_EQ(alignment % 16, 0);
+  int align_mask = (alignment / kWRegSizeInBytes) - 1;
+  num_wreg_to_allocate = (num_wreg_to_allocate + align_mask) & ~align_mask;
+
+  // Check if we have space on the stack.
+  Label stack_limit_hit;
+  Label stack_ok;
+
+  ExternalReference stack_limit =
+      ExternalReference::address_of_stack_limit(isolate());
+  __ Mov(x10, Operand(stack_limit));
+  __ Ldr(x10, MemOperand(x10));
+  __ Subs(x10, csp, x10);
+
+  // Handle it if the stack pointer is already below the stack limit.
+  __ B(ls, &stack_limit_hit);
+
+  // Check if there is room for the variable number of registers above
+  // the stack limit.
+  __ Cmp(x10, num_wreg_to_allocate * kWRegSizeInBytes);
+  __ B(hs, &stack_ok);
+
+  // Exit with OutOfMemory exception. There is not enough space on the stack
+  // for our working registers.
+  __ Mov(w0, EXCEPTION);
+  __ B(&return_w0);
+
+  __ Bind(&stack_limit_hit);
+  CallCheckStackGuardState(x10);
+  // If returned value is non-zero, we exit with the returned value as result.
+  __ Cbnz(w0, &return_w0);
+
+  __ Bind(&stack_ok);
+
+  // Allocate space on stack.
+  __ Claim(num_wreg_to_allocate, kWRegSizeInBytes);
+
+  // Initialize success_counter with 0.
+  __ Str(wzr, MemOperand(frame_pointer(), kSuccessCounter));
+
+  // Find negative length (offset of start relative to end).
+  __ Sub(x10, input_start(), input_end());
+  if (masm_->emit_debug_code()) {
+    // Check that the input string length is < 2^30.
+    __ Neg(x11, x10);
+    __ Cmp(x11, (1<<30) - 1);
+    __ Check(ls, "The length of the input string cannot be >= 2^30.");
+  }
+  __ Mov(current_input_offset(), w10);
+
+  // The non-position value is used as a clearing value for the
+  // capture registers, it corresponds to the position of the first character
+  // minus one.
+  __ Sub(non_position_value(), current_input_offset(), char_size());
+  __ Sub(non_position_value(), non_position_value(),
+         Operand(start_offset(), LSL, (mode_ == UC16) ? 1 : 0));
+  // We can store this value twice in an X register for initializing
+  // on-stack registers later.
+  __ Orr(twice_non_position_value(),
+         non_position_value().X(),
+         Operand(non_position_value().X(), LSL, kWRegSize));
+
+  // Initialize code pointer register.
+  __ Mov(code_pointer(), Operand(masm_->CodeObject()));
+
+  Label load_char_start_regexp, start_regexp;
+  // Load newline if index is at start, previous character otherwise.
+  __ Cbnz(start_offset(), &load_char_start_regexp);
+  __ Mov(current_character(), '\n');
+  __ B(&start_regexp);
+
+  // Global regexp restarts matching here.
+  __ Bind(&load_char_start_regexp);
+  // Load previous char as initial value of current character register.
+  LoadCurrentCharacterUnchecked(-1, 1);
+  __ Bind(&start_regexp);
+  // Initialize on-stack registers.
+  if (num_saved_registers_ > 0) {
+    ClearRegisters(0, num_saved_registers_ - 1);
+  }
+
+  // Initialize backtrack stack pointer.
+  __ Ldr(backtrack_stackpointer(), MemOperand(frame_pointer(), kStackBase));
+
+  // Execute
+  __ B(&start_label_);
+
+  if (backtrack_label_.is_linked()) {
+    __ Bind(&backtrack_label_);
+    Backtrack();
+  }
+
+  if (success_label_.is_linked()) {
+    Register first_capture_start = w15;
+
+    // Save captures when successful.
+    __ Bind(&success_label_);
+
+    if (num_saved_registers_ > 0) {
+      // V8 expects the output to be an int32_t array.
+      Register capture_start = w12;
+      Register capture_end = w13;
+      Register input_length = w14;
+
+      // Copy captures to output.
+
+      // Get string length.
+      __ Sub(x10, input_end(), input_start());
+      if (masm_->emit_debug_code()) {
+        // Check that the input string length is < 2^30.
+        __ Cmp(x10, (1<<30) - 1);
+        __ Check(ls, "The length of the input string cannot be >= 2^30.");
+      }
+      // input_start has a start_offset offset on entry. We need to include
+      // it when computing the length of the whole string.
+      if (mode_ == UC16) {
+        __ Add(input_length, start_offset(), Operand(w10, LSR, 1));
+      } else {
+        __ Add(input_length, start_offset(), w10);
+      }
+
+      // Copy the results to the output array from the cached registers first.
+      for (int i = 0;
+           (i < num_saved_registers_) && (i < kNumCachedRegisters);
+           i += 2) {
+        __ Mov(capture_start.X(), GetCachedRegister(i));
+        __ Lsr(capture_end.X(), capture_start.X(), kWRegSize);
+        if ((i == 0) && global_with_zero_length_check()) {
+          // Keep capture start for the zero-length check later.
+          __ Mov(first_capture_start, capture_start);
+        }
+        // Offsets need to be relative to the start of the string.
+        if (mode_ == UC16) {
+          __ Add(capture_start, input_length, Operand(capture_start, ASR, 1));
+          __ Add(capture_end, input_length, Operand(capture_end, ASR, 1));
+        } else {
+          __ Add(capture_start, input_length, capture_start);
+          __ Add(capture_end, input_length, capture_end);
+        }
+        // The output pointer advances for a possible global match.
+        __ Stp(capture_start,
+               capture_end,
+               MemOperand(output_array(), kPointerSize, PostIndex));
+      }
+
+      // Only carry on if there are more than kNumCachedRegisters capture
+      // registers.
+      int num_registers_left_on_stack =
+          num_saved_registers_ - kNumCachedRegisters;
+      if (num_registers_left_on_stack > 0) {
+        Register base = x10;
+        // There are always an even number of capture registers. A couple of
+        // registers determine one match with two offsets.
+        ASSERT_EQ(0, num_registers_left_on_stack % 2);
+        __ Add(base, frame_pointer(), kFirstCaptureOnStack);
+
+        // We can unroll the loop here, we should not unroll for less than 2
+        // registers.
+        STATIC_ASSERT(kNumRegistersToUnroll > 2);
+        if (num_registers_left_on_stack <= kNumRegistersToUnroll) {
+          for (int i = 0; i < num_registers_left_on_stack / 2; i++) {
+            __ Ldp(capture_end,
+                   capture_start,
+                   MemOperand(base, -kPointerSize, PostIndex));
+            if ((i == 0) && global_with_zero_length_check()) {
+              // Keep capture start for the zero-length check later.
+              __ Mov(first_capture_start, capture_start);
+            }
+            // Offsets need to be relative to the start of the string.
+            if (mode_ == UC16) {
+              __ Add(capture_start,
+                     input_length,
+                     Operand(capture_start, ASR, 1));
+              __ Add(capture_end, input_length, Operand(capture_end, ASR, 1));
+            } else {
+              __ Add(capture_start, input_length, capture_start);
+              __ Add(capture_end, input_length, capture_end);
+            }
+            // The output pointer advances for a possible global match.
+            __ Stp(capture_start,
+                   capture_end,
+                   MemOperand(output_array(), kPointerSize, PostIndex));
+          }
+        } else {
+          Label loop, start;
+          __ Mov(x11, num_registers_left_on_stack);
+
+          __ Ldp(capture_end,
+                 capture_start,
+                 MemOperand(base, -kPointerSize, PostIndex));
+          if (global_with_zero_length_check()) {
+            __ Mov(first_capture_start, capture_start);
+          }
+          __ B(&start);
+
+          __ Bind(&loop);
+          __ Ldp(capture_end,
+                 capture_start,
+                 MemOperand(base, -kPointerSize, PostIndex));
+          __ Bind(&start);
+          if (mode_ == UC16) {
+            __ Add(capture_start, input_length, Operand(capture_start, ASR, 1));
+            __ Add(capture_end, input_length, Operand(capture_end, ASR, 1));
+          } else {
+            __ Add(capture_start, input_length, capture_start);
+            __ Add(capture_end, input_length, capture_end);
+          }
+          // The output pointer advances for a possible global match.
+          __ Stp(capture_start,
+                 capture_end,
+                 MemOperand(output_array(), kPointerSize, PostIndex));
+          __ Sub(x11, x11, 2);
+          __ Cbnz(x11, &loop);
+        }
+      }
+    }
+
+    if (global()) {
+      Register success_counter = w0;
+      Register output_size = x10;
+      // Restart matching if the regular expression is flagged as global.
+
+      // Increment success counter.
+      __ Ldr(success_counter, MemOperand(frame_pointer(), kSuccessCounter));
+      __ Add(success_counter, success_counter, 1);
+      __ Str(success_counter, MemOperand(frame_pointer(), kSuccessCounter));
+
+      // Capture results have been stored, so the number of remaining global
+      // output registers is reduced by the number of stored captures.
+      __ Ldr(output_size, MemOperand(frame_pointer(), kOutputSize));
+      __ Sub(output_size, output_size, num_saved_registers_);
+      // Check whether we have enough room for another set of capture results.
+      __ Cmp(output_size, num_saved_registers_);
+      __ B(lt, &return_w0);
+
+      // The output pointer is already set to the next field in the output
+      // array.
+      // Update output size on the frame before we restart matching.
+      __ Str(output_size, MemOperand(frame_pointer(), kOutputSize));
+
+      if (global_with_zero_length_check()) {
+        // Special case for zero-length matches.
+        __ Cmp(current_input_offset(), first_capture_start);
+        // Not a zero-length match, restart.
+        __ B(ne, &load_char_start_regexp);
+        // Offset from the end is zero if we already reached the end.
+        __ Cbz(current_input_offset(), &return_w0);
+        // Advance current position after a zero-length match.
+        __ Add(current_input_offset(),
+               current_input_offset(),
+               Operand((mode_ == UC16) ? 2 : 1));
+      }
+
+      __ B(&load_char_start_regexp);
+    } else {
+      __ Mov(w0, SUCCESS);
+    }
+  }
+
+  if (exit_label_.is_linked()) {
+    // Exit and return w0
+    __ Bind(&exit_label_);
+    if (global()) {
+      __ Ldr(w0, MemOperand(frame_pointer(), kSuccessCounter));
+    }
+  }
+
+  __ Bind(&return_w0);
+
+  // Set stack pointer back to first register to retain
+  ASSERT(csp.Is(__ StackPointer()));
+  __ Mov(csp, fp);
+
+  // Restore registers.
+  __ PopCPURegList(registers_to_retain);
+
+  __ Ret();
+
+  Label exit_with_exception;
+  // Registers x0 to x7 are used to store the first captures, they need to be
+  // retained over calls to C++ code.
+  CPURegList cached_registers(CPURegister::kRegister, kXRegSize, 0, 7);
+  ASSERT((cached_registers.Count() * 2) == kNumCachedRegisters);
+
+  if (check_preempt_label_.is_linked()) {
+    __ Bind(&check_preempt_label_);
+    SaveLinkRegister();
+    // The cached registers need to be retained.
+    __ PushCPURegList(cached_registers);
+    CallCheckStackGuardState(x10);
+    // Returning from the regexp code restores the stack (csp <- fp)
+    // so we don't need to drop the link register from it before exiting.
+    __ Cbnz(w0, &return_w0);
+    // Reset the cached registers.
+    __ PopCPURegList(cached_registers);
+    RestoreLinkRegister();
+    __ Ret();
+  }
+
+  if (stack_overflow_label_.is_linked()) {
+    __ Bind(&stack_overflow_label_);
+    SaveLinkRegister();
+    // The cached registers need to be retained.
+    __ PushCPURegList(cached_registers);
+    // Call GrowStack(backtrack_stackpointer(), &stack_base)
+    __ Mov(x2, Operand(ExternalReference::isolate_address(isolate())));
+    __ Add(x1, frame_pointer(), kStackBase);
+    __ Mov(x0, backtrack_stackpointer());
+    ExternalReference grow_stack =
+        ExternalReference::re_grow_stack(isolate());
+    __ CallCFunction(grow_stack, 3);
+    // If return NULL, we have failed to grow the stack, and
+    // must exit with a stack-overflow exception.
+    // Returning from the regexp code restores the stack (csp <- fp)
+    // so we don't need to drop the link register from it before exiting.
+    __ Cbz(w0, &exit_with_exception);
+    // Otherwise use return value as new stack pointer.
+    __ Mov(backtrack_stackpointer(), x0);
+    // Reset the cached registers.
+    __ PopCPURegList(cached_registers);
+    RestoreLinkRegister();
+    __ Ret();
+  }
+
+  if (exit_with_exception.is_linked()) {
+    __ Bind(&exit_with_exception);
+    __ Mov(w0, EXCEPTION);
+    __ B(&return_w0);
+  }
+
+  CodeDesc code_desc;
+  masm_->GetCode(&code_desc);
+  Handle<Code> code = isolate()->factory()->NewCode(
+      code_desc, Code::ComputeFlags(Code::REGEXP), masm_->CodeObject());
+  PROFILE(Isolate::Current(), RegExpCodeCreateEvent(*code, *source));
+  return Handle<HeapObject>::cast(code);
+}
+
+
+void RegExpMacroAssemblerA64::GoTo(Label* to) {
+  BranchOrBacktrack(al, to);
+}
+
+void RegExpMacroAssemblerA64::IfRegisterGE(int reg,
+                                           int comparand,
+                                           Label* if_ge) {
+  Register to_compare = GetRegister(reg, w10);
+  CompareAndBranchOrBacktrack(to_compare, comparand, ge, if_ge);
+}
+
+
+void RegExpMacroAssemblerA64::IfRegisterLT(int reg,
+                                           int comparand,
+                                           Label* if_lt) {
+  Register to_compare = GetRegister(reg, w10);
+  CompareAndBranchOrBacktrack(to_compare, comparand, lt, if_lt);
+}
+
+
+void RegExpMacroAssemblerA64::IfRegisterEqPos(int reg,
+                                              Label* if_eq) {
+  Register to_compare = GetRegister(reg, w10);
+  __ Cmp(to_compare, current_input_offset());
+  BranchOrBacktrack(eq, if_eq);
+}
+
+RegExpMacroAssembler::IrregexpImplementation
+    RegExpMacroAssemblerA64::Implementation() {
+  return kA64Implementation;
+}
+
+
+void RegExpMacroAssemblerA64::LoadCurrentCharacter(int cp_offset,
+                                                   Label* on_end_of_input,
+                                                   bool check_bounds,
+                                                   int characters) {
+  // TODO(pielan): Make sure long strings are caught before this, and not
+  // just asserted in debug mode.
+  ASSERT(cp_offset >= -1);      // ^ and \b can look behind one character.
+  // Be sane! (And ensure that an int32_t can be used to index the string)
+  ASSERT(cp_offset < (1<<30));
+  if (check_bounds) {
+    CheckPosition(cp_offset + characters - 1, on_end_of_input);
+  }
+  LoadCurrentCharacterUnchecked(cp_offset, characters);
+}
+
+
+void RegExpMacroAssemblerA64::PopCurrentPosition() {
+  Pop(current_input_offset());
+}
+
+
+void RegExpMacroAssemblerA64::PopRegister(int register_index) {
+  Pop(w10);
+  StoreRegister(register_index, w10);
+}
+
+void RegExpMacroAssemblerA64::PushBacktrack(Label* label) {
+  if (label->is_bound()) {
+    int target = label->pos();
+    __ Mov(w10, target + Code::kHeaderSize - kHeapObjectTag);
+  } else {
+    __ Adr(x10, label);
+    __ Sub(x10, x10, code_pointer());
+    if (masm_->emit_debug_code()) {
+      __ Cmp(x10, kWRegMask);
+      __ Check(ls, "The code offset needs to fit in a W register.");
+    }
+  }
+  Push(w10);
+  CheckStackLimit();
+}
+
+
+void RegExpMacroAssemblerA64::PushCurrentPosition() {
+  Push(current_input_offset());
+}
+
+
+void RegExpMacroAssemblerA64::PushRegister(int register_index,
+                                           StackCheckFlag check_stack_limit) {
+  Register to_push = GetRegister(register_index, w10);
+  Push(to_push);
+  if (check_stack_limit) CheckStackLimit();
+}
+
+
+void RegExpMacroAssemblerA64::ReadCurrentPositionFromRegister(int reg) {
+  Register cached_register;
+  RegisterState register_state = GetRegisterState(reg);
+  switch (register_state) {
+    case STACKED:
+      __ Ldr(current_input_offset(), register_location(reg));
+      break;
+    case CACHED_LSW:
+      cached_register = GetCachedRegister(reg);
+      __ Mov(current_input_offset(), cached_register.W());
+      break;
+    case CACHED_MSW:
+      cached_register = GetCachedRegister(reg);
+      __ Lsr(current_input_offset().X(), cached_register, kWRegSize);
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+}
+
+
+void RegExpMacroAssemblerA64::ReadStackPointerFromRegister(int reg) {
+  Register read_from = GetRegister(reg, w10);
+  __ Ldr(x11, MemOperand(frame_pointer(), kStackBase));
+  __ Add(backtrack_stackpointer(), x11, Operand(read_from, SXTW));
+}
+
+
+void RegExpMacroAssemblerA64::SetCurrentPositionFromEnd(int by) {
+  Label after_position;
+  __ Cmp(current_input_offset(), -by * char_size());
+  __ B(ge, &after_position);
+  __ Mov(current_input_offset(), -by * char_size());
+  // On RegExp code entry (where this operation is used), the character before
+  // the current position is expected to be already loaded.
+  // We have advanced the position, so it's safe to read backwards.
+  LoadCurrentCharacterUnchecked(-1, 1);
+  __ Bind(&after_position);
+}
+
+
+void RegExpMacroAssemblerA64::SetRegister(int register_index, int to) {
+  ASSERT(register_index >= num_saved_registers_);  // Reserved for positions!
+  Register set_to = wzr;
+  if (to != 0) {
+    set_to = w10;
+    __ Mov(set_to, to);
+  }
+  StoreRegister(register_index, set_to);
+}
+
+
+bool RegExpMacroAssemblerA64::Succeed() {
+  __ B(&success_label_);
+  return global();
+}
+
+
+void RegExpMacroAssemblerA64::WriteCurrentPositionToRegister(int reg,
+                                                             int cp_offset) {
+  Register position = current_input_offset();
+  if (cp_offset != 0) {
+    position = w10;
+    __ Add(position, current_input_offset(), cp_offset * char_size());
+  }
+  StoreRegister(reg, position);
+}
+
+
+void RegExpMacroAssemblerA64::ClearRegisters(int reg_from, int reg_to) {
+  ASSERT(reg_from <= reg_to);
+  int num_registers = reg_to - reg_from + 1;
+  if ((num_registers % 2) == 1) {
+    StoreRegister(reg_from, non_position_value());
+    num_registers--;
+    reg_from++;
+  }
+  // Clear cached registers.
+  while ((reg_from <= reg_to) && (reg_from < kNumCachedRegisters)) {
+    ASSERT(GetRegisterState(reg_from) != STACKED);
+    __ Mov(GetCachedRegister(reg_from), twice_non_position_value());
+    reg_from += 2;
+    num_registers -= 2;
+  }
+  if (num_registers > 0) {
+    // Move down the indexes of the registers on stack to get the correct offset
+    // in memory.
+    reg_from -= kNumCachedRegisters;
+    reg_to -= kNumCachedRegisters;
+    // We should not unroll the loop for less than 2 registers.
+    STATIC_ASSERT(kNumRegistersToUnroll > 2);
+    // We position the base pointer to (reg_from + 1).
+    int base_offset = kFirstRegisterOnStack -
+        kWRegSizeInBytes - (kWRegSizeInBytes * reg_from);
+    if (num_registers > kNumRegistersToUnroll) {
+      Register base = x10;
+      __ Add(base, frame_pointer(), base_offset);
+
+      Label loop;
+      __ Mov(x11, num_registers);
+      __ Bind(&loop);
+      __ Str(twice_non_position_value(),
+             MemOperand(base, -kPointerSize, PostIndex));
+      __ Sub(x11, x11, 2);
+      __ Cbnz(x11, &loop);
+    } else {
+      for (int i = reg_from; i <= reg_to; i += 2) {
+        __ Str(twice_non_position_value(),
+               MemOperand(frame_pointer(), base_offset));
+        base_offset -= kWRegSizeInBytes * 2;
+      }
+    }
+  }
+}
+
+
+void RegExpMacroAssemblerA64::WriteStackPointerToRegister(int reg) {
+  __ Ldr(x10, MemOperand(frame_pointer(), kStackBase));
+  __ Sub(x10, backtrack_stackpointer(), x10);
+  if (masm_->emit_debug_code()) {
+    __ Cmp(x10, Operand(w10, SXTW));
+    __ Check(eq, "Offset from the stack base needs to fit in a W register.");
+  }
+  StoreRegister(reg, w10);
+}
+
+// Helper function for reading a value out of a stack frame.
+template <typename T>
+static T& frame_entry(Address re_frame, int frame_offset) {
+  return *reinterpret_cast<T*>(re_frame + frame_offset);
+}
+
+int RegExpMacroAssemblerA64::CheckStackGuardState(Address* return_address,
+                                                  Code* re_code,
+                                                  Address re_frame,
+                                                  int start_offset,
+                                                  const byte** input_start,
+                                                  const byte** input_end) {
+  Isolate* isolate = frame_entry<Isolate*>(re_frame, kIsolate);
+  ASSERT(isolate == Isolate::Current());
+  if (isolate->stack_guard()->IsStackOverflow()) {
+    isolate->StackOverflow();
+    return EXCEPTION;
+  }
+
+  // If not real stack overflow the stack guard was used to interrupt
+  // execution for another purpose.
+
+  // If this is a direct call from JavaScript retry the RegExp forcing the call
+  // through the runtime system. Currently the direct call cannot handle a GC.
+  if (frame_entry<int>(re_frame, kDirectCall) == 1) {
+    return RETRY;
+  }
+
+  // Prepare for possible GC.
+  HandleScope handles(isolate);
+  Handle<Code> code_handle(re_code);
+
+  Handle<String> subject(frame_entry<String*>(re_frame, kInput));
+
+  // Current string.
+  bool is_ascii = subject->IsOneByteRepresentationUnderneath();
+
+  ASSERT(re_code->instruction_start() <= *return_address);
+  ASSERT(*return_address <=
+      re_code->instruction_start() + re_code->instruction_size());
+
+  MaybeObject* result = Execution::HandleStackGuardInterrupt(isolate);
+
+  if (*code_handle != re_code) {  // Return address no longer valid
+    int delta = code_handle->address() - re_code->address();
+    // Overwrite the return address on the stack.
+    *return_address += delta;
+  }
+
+  if (result->IsException()) {
+    return EXCEPTION;
+  }
+
+  Handle<String> subject_tmp = subject;
+  int slice_offset = 0;
+
+  // Extract the underlying string and the slice offset.
+  if (StringShape(*subject_tmp).IsCons()) {
+    subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
+  } else if (StringShape(*subject_tmp).IsSliced()) {
+    SlicedString* slice = SlicedString::cast(*subject_tmp);
+    subject_tmp = Handle<String>(slice->parent());
+    slice_offset = slice->offset();
+  }
+
+  // String might have changed.
+  if (subject_tmp->IsOneByteRepresentation() != is_ascii) {
+    // If we changed between an ASCII and an UC16 string, the specialized
+    // code cannot be used, and we need to restart regexp matching from
+    // scratch (including, potentially, compiling a new version of the code).
+    return RETRY;
+  }
+
+  // Otherwise, the content of the string might have moved. It must still
+  // be a sequential or external string with the same content.
+  // Update the start and end pointers in the stack frame to the current
+  // location (whether it has actually moved or not).
+  ASSERT(StringShape(*subject_tmp).IsSequential() ||
+         StringShape(*subject_tmp).IsExternal());
+
+  // The original start address of the characters to match.
+  const byte* start_address = *input_start;
+
+  // Find the current start address of the same character at the current string
+  // position.
+  const byte* new_address = StringCharacterPosition(*subject_tmp,
+      start_offset + slice_offset);
+
+  if (start_address != new_address) {
+    // If there is a difference, update the object pointer and start and end
+    // addresses in the RegExp stack frame to match the new value.
+    const byte* end_address = *input_end;
+    int byte_length = static_cast<int>(end_address - start_address);
+    frame_entry<const String*>(re_frame, kInput) = *subject;
+    *input_start = new_address;
+    *input_end = new_address + byte_length;
+  } else if (frame_entry<const String*>(re_frame, kInput) != *subject) {
+    // Subject string might have been a ConsString that underwent
+    // short-circuiting during GC. That will not change start_address but
+    // will change pointer inside the subject handle.
+    frame_entry<const String*>(re_frame, kInput) = *subject;
+  }
+
+  return 0;
+}
+
+void RegExpMacroAssemblerA64::CheckPosition(int cp_offset,
+                                            Label* on_outside_input) {
+  CompareAndBranchOrBacktrack(current_input_offset(),
+                              -cp_offset * char_size(),
+                              ge,
+                              on_outside_input);
+}
+
+bool RegExpMacroAssemblerA64::CanReadUnaligned() {
+  // TODO(pielan): See whether or not we should disable unaligned accesses.
+  return !slow_safe();
+}
+
+// Private methods:
+
+void RegExpMacroAssemblerA64::CallCheckStackGuardState(Register scratch) {
+  // Allocate space on the stack to store the return address. The
+  // CheckStackGuardState C++ function will override it if the code
+  // moved. Allocate extra space for 2 arguments passed by pointers.
+  // AAPCS64 requires the stack to be 16 byte aligned.
+  int alignment = masm_->ActivationFrameAlignment();
+  ASSERT_EQ(alignment % 16, 0);
+  int align_mask = (alignment / kXRegSizeInBytes) - 1;
+  int xreg_to_claim = (3 + align_mask) & ~align_mask;
+
+  ASSERT(csp.Is(__ StackPointer()));
+  __ Claim(xreg_to_claim);
+
+  // CheckStackGuardState needs the end and start addresses of the input string.
+  __ Poke(input_end(), 2 * kPointerSize);
+  __ Add(x5, csp, 2 * kPointerSize);
+  __ Poke(input_start(), kPointerSize);
+  __ Add(x4, csp, kPointerSize);
+
+  __ Mov(w3, start_offset());
+  // RegExp code frame pointer.
+  __ Mov(x2, frame_pointer());
+  // Code* of self.
+  __ Mov(x1, Operand(masm_->CodeObject()));
+
+  // We need to pass a pointer to the return address as first argument.
+  // The DirectCEntry stub will place the return address on the stack before
+  // calling so the stack pointer will point to it.
+  __ Mov(x0, csp);
+
+  ExternalReference check_stack_guard_state =
+      ExternalReference::re_check_stack_guard_state(isolate());
+  __ Mov(scratch, Operand(check_stack_guard_state));
+  DirectCEntryStub stub;
+  stub.GenerateCall(masm_, scratch);
+
+  // The input string may have been moved in memory, we need to reload it.
+  __ Peek(input_start(), kPointerSize);
+  __ Peek(input_end(), 2 * kPointerSize);
+
+  ASSERT(csp.Is(__ StackPointer()));
+  __ Drop(xreg_to_claim);
+
+  // Reload the Code pointer.
+  __ Mov(code_pointer(), Operand(masm_->CodeObject()));
+}
+
+void RegExpMacroAssemblerA64::BranchOrBacktrack(Condition condition,
+                                                Label* to) {
+  if (condition == al) {  // Unconditional.
+    if (to == NULL) {
+      Backtrack();
+      return;
+    }
+    __ B(to);
+    return;
+  }
+  if (to == NULL) {
+    __ B(condition, &backtrack_label_);
+    return;
+  }
+  __ B(condition, to);
+}
+
+void RegExpMacroAssemblerA64::CompareAndBranchOrBacktrack(Register reg,
+                                                          int immediate,
+                                                          Condition condition,
+                                                          Label* to) {
+  if ((immediate == 0) && ((condition == eq) || (condition == ne))) {
+    if (to == NULL) {
+      to = &backtrack_label_;
+    }
+    if (condition == eq) {
+      __ Cbz(reg, to);
+    } else {
+      __ Cbnz(reg, to);
+    }
+  } else {
+    __ Cmp(reg, immediate);
+    BranchOrBacktrack(condition, to);
+  }
+}
+
+
+void RegExpMacroAssemblerA64::CheckPreemption() {
+  // Check for preemption.
+  ExternalReference stack_limit =
+      ExternalReference::address_of_stack_limit(isolate());
+  __ Mov(x10, Operand(stack_limit));
+  __ Ldr(x10, MemOperand(x10));
+  ASSERT(csp.Is(__ StackPointer()));
+  __ Cmp(csp, x10);
+  CallIf(&check_preempt_label_, ls);
+}
+
+void RegExpMacroAssemblerA64::CheckStackLimit() {
+  ExternalReference stack_limit =
+      ExternalReference::address_of_regexp_stack_limit(isolate());
+  __ Mov(x10, Operand(stack_limit));
+  __ Ldr(x10, MemOperand(x10));
+  __ Cmp(backtrack_stackpointer(), x10);
+  CallIf(&stack_overflow_label_, ls);
+}
+
+
+void RegExpMacroAssemblerA64::Push(Register source) {
+  ASSERT(source.Is32Bits());
+  ASSERT(!source.is(backtrack_stackpointer()));
+  __ Str(source,
+         MemOperand(backtrack_stackpointer(),
+                    -static_cast<int>(kWRegSizeInBytes),
+                    PreIndex));
+}
+
+void RegExpMacroAssemblerA64::Pop(Register target) {
+  ASSERT(target.Is32Bits());
+  ASSERT(!target.is(backtrack_stackpointer()));
+  __ Ldr(target,
+         MemOperand(backtrack_stackpointer(), kWRegSizeInBytes, PostIndex));
+}
+
+
+Register RegExpMacroAssemblerA64::GetCachedRegister(int register_index) {
+  ASSERT(register_index < kNumCachedRegisters);
+  return Register(register_index / 2, kXRegSize);
+}
+
+
+Register RegExpMacroAssemblerA64::GetRegister(int register_index,
+                                              Register maybe_result) {
+  ASSERT(maybe_result.Is32Bits());
+  ASSERT(register_index >= 0);
+  if (num_registers_ <= register_index) {
+    num_registers_ = register_index + 1;
+  }
+  Register result;
+  RegisterState register_state = GetRegisterState(register_index);
+  switch (register_state) {
+    case STACKED:
+      __ Ldr(maybe_result, register_location(register_index));
+      result = maybe_result;
+      break;
+    case CACHED_LSW:
+      result = GetCachedRegister(register_index).W();
+      break;
+    case CACHED_MSW:
+      __ Lsr(maybe_result.X(), GetCachedRegister(register_index), kWRegSize);
+      result = maybe_result;
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+  ASSERT(result.Is32Bits());
+  return result;
+}
+
+
+void RegExpMacroAssemblerA64::StoreRegister(int register_index,
+                                            Register source) {
+  ASSERT(source.Is32Bits());
+  ASSERT(register_index >= 0);
+  if (num_registers_ <= register_index) {
+    num_registers_ = register_index + 1;
+  }
+
+  Register cached_register;
+  RegisterState register_state = GetRegisterState(register_index);
+  switch (register_state) {
+    case STACKED:
+      __ Str(source, register_location(register_index));
+      break;
+    case CACHED_LSW:
+      cached_register = GetCachedRegister(register_index);
+      if (!source.Is(cached_register.W())) {
+        __ Bfi(cached_register, source.X(), 0, kWRegSize);
+      }
+      break;
+    case CACHED_MSW:
+      cached_register = GetCachedRegister(register_index);
+      __ Bfi(cached_register, source.X(), kWRegSize, kWRegSize);
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+}
+
+
+void RegExpMacroAssemblerA64::CallIf(Label* to, Condition condition) {
+  Label skip_call;
+  if (condition != al) __ B(&skip_call, InvertCondition(condition));
+  __ Bl(to);
+  __ Bind(&skip_call);
+}
+
+
+void RegExpMacroAssemblerA64::RestoreLinkRegister() {
+  ASSERT(csp.Is(__ StackPointer()));
+  __ Pop(lr, xzr);
+  __ Add(lr, lr, Operand(masm_->CodeObject()));
+}
+
+
+void RegExpMacroAssemblerA64::SaveLinkRegister() {
+  ASSERT(csp.Is(__ StackPointer()));
+  __ Sub(lr, lr, Operand(masm_->CodeObject()));
+  __ Push(xzr, lr);
+}
+
+
+MemOperand RegExpMacroAssemblerA64::register_location(int register_index) {
+  ASSERT(register_index < (1<<30));
+  ASSERT(register_index >= kNumCachedRegisters);
+  if (num_registers_ <= register_index) {
+    num_registers_ = register_index + 1;
+  }
+  register_index -= kNumCachedRegisters;
+  int offset = kFirstRegisterOnStack - register_index * kWRegSizeInBytes;
+  return MemOperand(frame_pointer(), offset);
+}
+
+MemOperand RegExpMacroAssemblerA64::capture_location(int register_index,
+                                                     Register scratch) {
+  ASSERT(register_index < (1<<30));
+  ASSERT(register_index < num_saved_registers_);
+  ASSERT(register_index >= kNumCachedRegisters);
+  ASSERT_EQ(register_index % 2, 0);
+  register_index -= kNumCachedRegisters;
+  int offset = kFirstCaptureOnStack - register_index * kWRegSizeInBytes;
+  // capture_location is used with Stp instructions to load/store 2 registers.
+  // The immediate field in the encoding is limited to 7 bits (signed).
+  if (is_int7(offset)) {
+    return MemOperand(frame_pointer(), offset);
+  } else {
+    __ Add(scratch, frame_pointer(), offset);
+    return MemOperand(scratch);
+  }
+}
+
+void RegExpMacroAssemblerA64::LoadCurrentCharacterUnchecked(int cp_offset,
+                                                            int characters) {
+  Register offset = current_input_offset();
+
+  // The ldr, str, ldrh, strh instructions can do unaligned accesses, if the CPU
+  // and the operating system running on the target allow it.
+  // If unaligned load/stores are not supported then this function must only
+  // be used to load a single character at a time.
+
+  // ARMv8 supports unaligned accesses but V8 or the kernel can decide to
+  // disable it.
+  // TODO(pielan): See whether or not we should disable unaligned accesses.
+  if (!CanReadUnaligned()) {
+    ASSERT(characters == 1);
+  }
+
+  if (cp_offset != 0) {
+    if (masm_->emit_debug_code()) {
+      __ Mov(x10, cp_offset * char_size());
+      __ Add(x10, x10, Operand(current_input_offset(), SXTW));
+      __ Cmp(x10, Operand(w10, SXTW));
+      __ Check(eq, "The offset needs to fit in a W register.");
+    } else {
+      __ Add(w10, current_input_offset(), cp_offset * char_size());
+    }
+    offset = w10;
+  }
+
+  if (mode_ == ASCII) {
+    if (characters == 4) {
+      __ Ldr(current_character(), MemOperand(input_end(), offset, SXTW));
+    } else if (characters == 2) {
+      __ Ldrh(current_character(), MemOperand(input_end(), offset, SXTW));
+    } else {
+      ASSERT(characters == 1);
+      __ Ldrb(current_character(), MemOperand(input_end(), offset, SXTW));
+    }
+  } else {
+    ASSERT(mode_ == UC16);
+    if (characters == 2) {
+      __ Ldr(current_character(), MemOperand(input_end(), offset, SXTW));
+    } else {
+      ASSERT(characters == 1);
+      __ Ldrh(current_character(), MemOperand(input_end(), offset, SXTW));
+    }
+  }
+}
+
+#endif  // V8_INTERPRETED_REGEXP
+
+}}  // namespace v8::internal
+
+#endif  // V8_TARGET_ARCH_A64